From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48E59C31E4A for ; Thu, 13 Jun 2019 16:28:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21CF420449 for ; Thu, 13 Jun 2019 16:28:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560443312; bh=xIY3VIlTtPhkqtybP4/9ZX6GyFeCo7yhrVUEIdByHJI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YWAhnKaQXqXw+4sJwdUgJ31/sBhiGCVyEG825q7gKTT3WPqY5j2lKkeTByjhpTrKs mdWNnGSK8wJ90YQ++K2xV1mA6rSYk4QThmxdsAQ+zeS7tT9kAE8f8dngwFLNGq+ljj 3Ej/CnkguM7yElNkjVo7Qnj9Wr7LVKv0V4td65GI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403931AbfFMQ2a (ORCPT ); Thu, 13 Jun 2019 12:28:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:53424 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730945AbfFMIfr (ORCPT ); Thu, 13 Jun 2019 04:35:47 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C694620851; Thu, 13 Jun 2019 08:35:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560414946; bh=xIY3VIlTtPhkqtybP4/9ZX6GyFeCo7yhrVUEIdByHJI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jg2UMoAm8Z7EdpSHxk4ZQn3uWbGry9yk+xtOwuYWfayYTGzUrkVEhyyqvw6KdMwst 24rjBVffxdYXdYRrn2jwGqYeL5X3vPyf5mVad/4u4+ylqGAo7QeJS2I7OfnvKldgML 9UzpXieYg00WeQADx5U+Cnq8P9ugyHrpj2niEFMY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Qian Cai , Andrew Morton , Vlastimil Babka , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Linus Torvalds , Sasha Levin Subject: [PATCH 4.14 12/81] mm/slab.c: fix an infinite loop in leaks_show() Date: Thu, 13 Jun 2019 10:32:55 +0200 Message-Id: <20190613075649.972724355@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190613075649.074682929@linuxfoundation.org> References: <20190613075649.074682929@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Upstream commit 745e10146c31b1c6ed3326286704ae251b17f663 ] "cat /proc/slab_allocators" could hang forever on SMP machines with kmemleak or object debugging enabled due to other CPUs running do_drain() will keep making kmemleak_object or debug_objects_cache dirty and unable to escape the first loop in leaks_show(), do { set_store_user_clean(cachep); drain_cpu_caches(cachep); ... } while (!is_store_user_clean(cachep)); For example, do_drain slabs_destroy slab_destroy kmem_cache_free __cache_free ___cache_free kmemleak_free_recursive delete_object_full __delete_object put_object free_object_rcu kmem_cache_free cache_free_debugcheck --> dirty kmemleak_object One approach is to check cachep->name and skip both kmemleak_object and debug_objects_cache in leaks_show(). The other is to set store_user_clean after drain_cpu_caches() which leaves a small window between drain_cpu_caches() and set_store_user_clean() where per-CPU caches could be dirty again lead to slightly wrong information has been stored but could also speed up things significantly which sounds like a good compromise. For example, # cat /proc/slab_allocators 0m42.778s # 1st approach 0m0.737s # 2nd approach [akpm@linux-foundation.org: tweak comment] Link: http://lkml.kernel.org/r/20190411032635.10325-1-cai@lca.pw Fixes: d31676dfde25 ("mm/slab: alternative implementation for DEBUG_SLAB_LEAK") Signed-off-by: Qian Cai Reviewed-by: Andrew Morton Cc: Vlastimil Babka Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/slab.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/slab.c b/mm/slab.c index 843ecea9e336..a04aeae42306 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -4320,8 +4320,12 @@ static int leaks_show(struct seq_file *m, void *p) * whole processing. */ do { - set_store_user_clean(cachep); drain_cpu_caches(cachep); + /* + * drain_cpu_caches() could make kmemleak_object and + * debug_objects_cache dirty, so reset afterwards. + */ + set_store_user_clean(cachep); x[1] = 0; -- 2.20.1